[Weapons] Build Your Own Classic Crossbow

It was the "hot setup" during the Crusades

. . . and it's going through a new revolution today.

The Classic Crossbow:You Can Build An archer might consider it kin to a firearm . . a shooter, on the other hand, most likely would think it a stock-mounted bow. and you wouldn't need a poll to know the general public's feeling: It looks sinister enough to be a lethal weapon! In short, there's not much doubt that the modem crossbow suffers an "identity crisis," but-regardless of the mystery that still surrounds this curious hybrid-it's been gaining in popularity among hunters and targeteers alike . . .and that trend hasn't gone unnoticed here at MOTHER. With several avid bowhunters on the staff, and a research department eager to take on such an interesting challenge, it wasn't too difficult to get the ball rolling on a project that we figured might be a first in the field: designing and building a quality crossbow testing its range, accuracy, from scratch and overall effectiveness . . . and then comparing its performance to that of traditional recurve and compound bows.

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ABOVE: Our fieldpiece looks-andf functions -like many of the more expensive manufactured crossbows. RIGHT: The front sight is a strap of aluminum fitted with a bead. The steel cocking rodgives the cocking lever (BELOW) a forward mount when the string is being drawn. FAR BELOW: i'2isprototype has no trigger safety, but one can be added.

A QUICK ANALYSIS The contemporary crossbow shares little beyond a basic design with its forebear, the medieval arbalest. Though both launch arrows (bolts) by means of a short bow transversely futed to a stock, the superiority of modem materials-along with the improved geometry made possible by the use of such lightweight plastics, alloys, and compositeshas turned what was a crude but effective weapon of war into an admirable piece of fairly uncomplicated technology. Over the past few years, crossbow design has received considerable attention from various manufacturers, with the result that the old standard has been modified to run the gamut from a paramilitary-looking assault piece to an artistic expression of classical physics. And although these developments represent improvement in most cases, they're beyond the ability of all but the best-equipped crafts people to duplicate. We chose the path of least resistance and used the simplest common denominators in our design. The stock of our crossbow consists of a center spine covered on each side by a strengthening flank. As a bolted-together unit, this flat-aluminum assembly serves as a combination barrel (or chase in crossbow terminology), trigger housing, handgrip, and shoulder extension. ' The bow, or prod, is set into the nose of the forestock, and the two-piece trigger mechanism, cut from 114" plate steel, is pinned between the right and left flank pieces just below the receiver. Walnut stock inserts were trimmed and shaped to mate with the stock

NOTE: Though we did build and test both of our crossbows, the potential for injury from any weapon is enough to compel us lo say that whoever builds and uses this tool does so at his or her own risk.

Your Own!

on either side of the shoulder extension. NOSE DETAIL Since the string does contact the barrel and is thus subject to friction, we added a pair of shoulder slides to the sides of the chase to reduce string wear and increase bolt velocity. Though these could also be made of walnut, we used Delrin (a Du Pont acetal resin) because it possesses an inherent lubricity. Our crossbow's open sights consist simply of a front frame made of aluminum strap, and an alloy rear ring mounted to the receiver, Socket-head cap screws threaded into each of these brackets provide sighting beads, and the rear unit can be lowered or raised as necessary to zero the piece in at a specific range. As far as we've been able to determine, a telescopic rifle sight is inappropriate on a crossbow for three reasons. First, the weap114' $1' x 1-114' on's effective range is limited to 50 yards or ALUMINUM PROD BLCXX so in all but an expert's hands, and at that distance, beads and the practiced naked eye The takedown version is either a pistol or a lot~garm. should be sufficient. Second, a fired bolt's TRIGGER AND SAFRY DETAIL trajectory is such that, beyond 15 or more NO 632 X 1-1R' SOW(ET+lEAD 025' X 318' X 3' yards, its drop is enough to lower the point CAP SCREW SIGHTING POST SPRINGSTEELTANG of impact many inches from the line of sight (see sidebar) . . . and since most scopes are calibrated for rifles, the range of adjustment may be restrictive or the zeroing-in process tedious. Finally, a scope narrows the field of view and adds weight as well. You've probably already noticed that our photos show two different crossbows. The / first, detailed in this article, is a functional, no-gadget rendition that's not overly complicated to assemble, which should serve as a fine fieldpiece or target piece. The second is a multiuse version that has some interesting features, but for the most part it's best suited to range shooting or backyard "plinking." It sports a folding front handgrip, a remov(3) In' X 3 4 ' EXPANSION PINS able shoulder stock extension (which allows lySrl' STEEL TRIGGER the long arm to convert to a hand piece), and -no doubt the most practical feature of all-a '5i32' X 1 'COMPRESSION SPRING positive trigger safety. (This last item, by the (10) NO. 6 X 314' W I N E SCREWS way, can be added to our standard crossbow if desired.) --

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PIECE BY PIECE You might be interested to know that we spent about $102 making our fieldpiece; that breaks down to approximately $14 worth of 114" aluminum flat stock (available at a scrapyard or a metals distributor); $8 in Delrin; $6 for the walnut billets; about $7 in assorted bolts, pins, and other minor hardware; and-here's the kicker-$67 worth of prod and Dacron bowstring. Admittedly, it would have been nice if we'd been able to construct our own short bow by using common materials .and believe us, (continued on next page)

COCKINQ LEVER (3) 114' X 314' MACHINE BOLTS

2) 118' X 1 ' X 24' FLAT-STEEL HANDLES

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l l B ' X 1 ' X 5112' FLATSTEEL COLLAR

114' X 1 ' MACHINE BOLTS

he Crossbow: Fact and Fiction Just how effective is a crossbow? To answer that question, several of MOTHER'S staffers took to the field with our project prototype equipped with a 175-pound prod . . . the smaller takedown model with a 75-pound draw weight. . . a $449 Bamett Commando (a quality commercial crossbow) rated at 175 pounds . . . a recurve bow rated at 54 pounds, full (30") draw. . . and a 7Gpound compound bow. We were interested in each weapon's range, accuracy, and penetrating power. . . but, ultimately, we were searching for the crossbow's proper niche in the order of things. Now we weren't interested in testing headto-head with the Barnett offering, and we couldn 't fairly pit a hand-held bow against a brace-mounted crossbow. So what we did was make a series of test firings with our standard model at distances of- 10,. 20,. 30,. 40, and 50 measured yardr. Each group consisted of five shots with the same 24.94-gram overall (126.3-grainfield point) Easton 14" aluminum bolt, and the resulting patterns then were measured and recorded. The crossbow was mounted and leveled in a sturdy brace, and a surueyor's transit was used to establish a direct line of sight to a given point on the target. The deviation of the points of impact from the sighting point was also noted. Wind conditions were fairly calm throughout the test. The chart below encapsulates our findings. As you can see, the homemade crossbow held a respectable pattern, even out to 50 yards. (We suspect it would do the same beyond that point, but thar's considered expert's range.) A t that distance, drop was considerable (i.e., the weapon's barrel would have to be elevated in order to hit a target in a level line of sight) . but the same situation existed in

thecaseofthe more traditionalhand-heldbows. Penetration was never a problem with any of the weapons we tested, since all the shafts buried themselves-some to the fletchingin the 12" of extruded polystyrene we used for a target backing. Considering the difference in draw weights between the traditional bows and the crossbows (and accounting for the standard arrows' additional mass), we could infer that prod strengths of more than 125pounds amount to overkill; the extra power probably offers little, but taxes strings, bolts, and cocking convenience heavily. Howmer, an understrength prod would be even less desirable unless it was matched with a short, lkht bolt. Our takedown ~ i s t o l model uses %-pound prod and a 6;' aluminum bolt, and has a power stroke of 6-1/4" compared to the larger weapon's 8-1/2". . fine for target shooting, but not really useful for hunting. Regardless of draw weight, string life can be extended and bolt velocity increased slightly by applying a lubniative wax to the string and the barrel's shoulder slides. In summary, much as we hate to burst a romantic balloon, we'll have to concede to the facts: Although a crossbow has the advantages of compactness and mechanical cocking and locking (it can be held at full draw without strain on the user), it is really no more accurate than a conventional bow in proficient hands . . . can't be loaded and fired as quickly . . and doesn't even approach the overall effectiveness of a rifle. Nonetheless, it's a valid sporting tool that's slowly but surely coming into its own once again.

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(continued from preceding page) we tried! But the laminated fiberglass prods we laid up just didn't have adequate draw strength or the resiliency to stand up to repeated use, possibly because we weren't able to duplicate the heat-and-pressure curing process used by commercial manufacturers. At any rate, we were pleased to learn that Barnett International (1967 Gunn Hwy., P.O. Box 934, Odessa, FL 33556) will sell prods, strings, bolts, and other accessories to anyone who orders the company's $2.00 postpaid catalog. T o ease construction, we've outlined the crossbow's major pans and drilling points within a grid, which will allow you to make up-scaled templates for the metal pieces. But play it safe by matching the templates perfectly before taping them to the metal and scribing theit outline . . . and be even more carehl when actually cutting the aluminum I stock, since [I] the pieces must join closely, or you'll be spending a lot of time with the FIELD TEST RESULTS OVERALL LENGTH: 31" file, and [2] the center spine's weak spotMODEL TESTED: Homemade, aluminum frame; OVERALL WIDTH: 26" the trigger guard-should not be any thinner walnut inserts; Delrin shoulder slides POWER STROKE: 8112" 7/32". than PROD: Barnett Commando, heatlpressurecured SIGHTS: Open, adjustable rear post The best way to trim the parts accurately, fiberglass, 175-pounddraw BOLT: Easton, 14" aluminum, 24.94 grams overall by the way, is to use a band saw equipped WEIGHT: 6 pounds, 5-112 ounces including 126.3-grain fieldpoint with a metal-cutting blade. Because the smooth operation of the trigger and string AVERAGE catch depends in great measure upon the perAVERAGE WINDAGE fect alignment of the three stock components, RANGE DROP ERROR PATTERN NOTES we suggest that you postpone drilling the 10 yds. +I' full penetration 314' flank pieces until you've bored the 9/64" post '14 yds. 0 rsm trajectory point holes according to the center points indicat20 yds. 11.114' tight pattern 5' 30 yds. 30" 9.iM' ed on the template. Once those sockets are bolt wobble t30 yd8. 21.112" 8' Its8 bolt wobble complete, clamp the aluminum center spine 40 yds. 50.314' 6.314' pattern improved to one of the flanks and recheck the align50 yds. 83' 6' more pattern Improvemen(; ment, using the template cutout from the trigrxcellmt penetration ger housing. Then drill corresponding holes Zero trajectory point t Barnett Commando comparison in the one flank piece.

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With that done, use No. 6 X 314" machine screws as temporary locating pins for the two bored components, and clamp the second flank piece in place. When you're satisfied that all three parts are evenly mated, drill the final member. Since the post screws are recessed, you'll need to countersink the exterior openings with larger bits according to the design ofthe screws and nuts you've chosen. The steel trigger components have to be thinned by 1164" in order to allow them freedom of movement within the stock. Once this is done, those parts can be drilled where indicated with a 118" bit, and the 1/8" X 314" expansidn pin pivots can be pressed in and centered. The pivot pins ride in 9/64" sockets drilled into the right and left flank pieces; to be on the safe side, you might want to use the trigger-housing template cutout to position those openings accurately. As we mentioned before, you can install a trigger safety mechanism according to our detail. Both the trigger and the safety catch are returned by small compression springs set into slots c i t through the central spine. Before assembling the stock for good, you'll want to bevel the inner surfaces of the barrel, and round the entire frame's outer edges. The rough work can be done with a grinder or file, and rhe metal then can be smoothed with emery cloth. Save the final extra-fine polishing for later, after you've bolted and pinned everything together and completed the cosmetic work. The next portion of the project includes setting the bolt tang (the spring-steel leaf that holds the projectile snug against the barrel), adding the wooden (or Delrin) slides to the flanks, and cutting, shaping, and fastening the walnut inserts that dress the shoulder extension. (These pieces can be cut to shape using

the template as a guide, then rounded with a sander and bolted or glued to the aluminum spine prior to being finished with varnish or tung oil.) The front sight is a piece of 1116" X 518" X 6-112" strap aluminum bent into an open frame configuration so the bolt can pass through it. It's fastened to the top of the forestock with two No. 6 X 1/4" machine screws, and a short cap screw locked through its crown serves as a bead. Though we used a machined ring at the rear (to provide a housing for an experimental scope sight), you can make an excellent sighting post by simply drilling and tapping a hole at the top of the receiver to accept a 6-32 socket-head cap screw about 1-112" in length. This can then be adjusted up or down for sighting. We ordered a prod with a draw strength of 175 pounds . . . but even if you choose a lighter bow to lengthen string life, you'll probably need a cocking lever to pull it into position. You can make one by bending four sections of 118" X 1" flat metal to create a two-armed, bolt-together yoke that uses mechanical advantage to ease cocking (see illustration). A pair of slots in the stationary part of the lever hook into a 5116" X 3" steel rod fitted into rhe crossbow's forestock (this should be located as indicated on the template and pressed in place before you install the prod), and another set of slots cut into the short "jack zrms" catch the string. The fulcrum's just a movable collar that can be locked into the optimal position. The prod is held in place by a 114" X 1" X 1-114" block of aluminum famd with a strip of hard rubber. A similar pad, glued to the rear of the prod socket, provides additional cushioning, and the metal block is forced tightly against the bow's face by a 114" X

1-314'' cap screw threaded into a tapped hole at the nose of the stock. Once the prod's installed, you'll have the pleasure of stringing it. Unless you're extraordinarily muscular, we'd suggest you purchase what's called a bastard string along with the regular Dacron cable. This set of strands is longer than the service string and thus can be slipped onto the prod more easily. It's then used to draw the bow's ears back to the cocked position so the real string can be looped in place. When that's done, both strings can be released with the trigger and the bastard removed. This is the only situation in which the crossbow should be "dry fired," since that practice car! split the prod. It should be quite obvious that your finished project has a lethal potential and should be handled with the same caution that you'd give to any longbow or firearm. Don't load it until you're ready to fire it, and don't fire it without an adequate field behind your target to safely absorb any overshots. Too, if you're interested in exploring the crossbow's capabilities for hunting, check your state's game laws before you build . . . it could save a lot of disappointment later. Meanwhile, you might want to look over the sidebar accompanying this article to see what kind of results you could expect from your modernday arbalest! EDITOR'S NOTE: I f you're intaesred in making the croshaofearured here (or the smaller rakedown version) bur would prefer detailed, step-by-step insrrucrionh a set of building plans-complete wirh full-size curring te7nplates -is available at a cost of $10 plus $1.00 for shipping and handling from Mother's Plans, Crossbows, P.O. Box A, East Flat Rock, NC 28726.8